The invention relates to an endless flexible torque-transmitting device with links that are connected to force-transfer elements, as used in particular in a continuously variable transmission of a motor vehicle where the endless flexible torque-transmitting device is arranged in the torque flow between a first and a second pair of conical disks. The force-transfer elements, serving to transmit lengthwise-oriented forces, are distributed at intervals along a circumference of the endless flexible torque-transmitting device. The links have openings that are traversed by the force-transfer elements, whereby columns of links are formed in the lengthwise direction of the endless flexible torque-transmitting device and the number and widths of the columns in the transverse direction define the width of the endless flexible torque-transmitting device.
Endless flexible torque-transmitting devices of this kind are known from the German patent DE-PS 33 24 318, among others. Link chains in accordance with the referenced patent are made up of fcrce-transfer elements that may comprise a single element or a set of at least two rocker elements that roll on each other. The force-transfer elements are in compressive contact with the conical disks, employing the frictional forces between the force-transfer elements and the conical disks to transmit a torque from the first to the second pair of conical disks. The transmission ratio can be increased or decreased in a continuous range by varying the distance between the disks in each pair of conical disks. The force-transfer elements are connected to each other through links. The connection is made by means of openings in the links through which the force-transfer elements extend. To optimally distribute the forces transmitted by the endless flexible torque-transmitting device, a multitude of links is used with each force-transfer element. In most cases, the links are arranged in a triple-link array, as described in the German patent 30 27 834, to reduce noise and achieve small chain radii and to thereby increase the transmission ratio.
Because the force-transfer elements have only a finite stiffness and because of system vibrations, the links carry unequal loads, which leads to the destruction of links primarily in the border zones. Doubling up the most highly stressed links or reinforcing them by increasing their thickness or by increasing the strength of the link material alleviates the problem, but then, with arrangements of this kind, the breakage of links will occur primarily in the immediate vicinity of the reinforcement. Thus, the aforementioned measures do not assure an unequivocal improvement, because they cannot fully compensate for the non-uniformity of the load distribution, meaning that the distribution of the tensile forces is still not sufficiently homogeneous. In addition, when using reinforced links, the reproducibility of the hardening process between the different kinds of links is poor, so that the quality assurance with regard to the dimensional integrity of the endless flexible torque-transmitting device becomes more difficult and manufacturing costs are increased because the parts have to be inspected.